Short answer, the global bitcoin market as a whole is still very small and immature. Market forces that would correct this kind of thing haven't kicked in enough yet to close this spread.

To get a sense of how small bitcoin still is with the 4 billion USD market cap seen as late, remember that Twitter recently had an IPO followed by trading on the open market where its market cap went up by several tens of billions all on the opening day!

The situation MtGox has themselves in is itself a good illustration of how immature the bitcoin space is, other asset classes don't have major exchanges that can't find a decent banking partner. Blame some of this on MtGox, blame some of this on the fact that they've got themselves involved in a strange new thing called bitcoin.

But, with there being other exchanges, it all goes beyond that: in a more mature market, it shouldn't matter that MtGox is only able to do 10 wire transfers per day and that their SEPA withdrawals are slow too. They have decent Yen withdrawal, folks who don't want a long wait should be bringing their bitcoin elsewhere to sell.

Arbitragers in Japan with access to this should be wiring their funds to Bitstamp and BTC-e, buying bitcoin, selling on Gox and getting Yen back fast. A well enough resourced person could even borrow bitcoin to sell on Gox at the same time as their buy on Bitstamp so that bitcoin network transfer times don't become a factor. Unlike China, I don't think Japan has a capital control situation that makes this too hard for wealthy and resourced Japanese folks to pull off.

But there is another factor at play, any arbitrager has to look at the depth of the order books to see what really can be done, prices at the top of the order books can't be the only indicator.

In a more mature market, some of the forces I've mentioned will close these gaps between exchanges. In time they probably will.

But that's the thing about market forces, they don't act as fast as they are sometimes idealized to. We're all very spoiled by how very fast bitcoin transfers are.

Let's put this basic fact about the pace of market forces in perspective. Labour markets are perhaps one of the best examples of those that are incredibly slow. Try cutting wages in absolute terms in a deflationary environment -- as an employer you'll have a riot on your hands even if your cuts are well below the deflation rate (higher wages in real terms). Try convincing a friend to leave all their social ties behind and move for employment opportunities to another region in the same country. Try retraining for a new career.